Dual-Substructure Measurement System for EUV Lithography Thermal Stability
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Solution Overview
Problem
Existing EUV projection exposure apparatuses for semiconductor lithography face challenges in maintaining precise positioning of optical elements due to thermal and magnetic influences, which affect imaging quality and require stiff and thermally stable measurement structures, often made from difficult-to-machine materials like SiSiC.
Innovation Solution
A dual-substructure measurement system where one substructure has a low coefficient of thermal expansion for long-term precision and the other has high stiffness for quick position changes, allowing for signal weighting to optimize position determination and reduce thermal and magnetic interference, potentially replacing materials like SiSiC and simplifying thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measurement structure is made stiff with high natural frequencies to prevent oscillation, then dynamic control and measurement accuracy are improved, but the structure becomes more sensitive to thermal expansion and requires complex thermal management
Solution Approach 1:
The measurement structure is divided into two mechanically decoupled substructures: a first substructure with low thermal expansion coefficient for long-term position stability, and a second substructure with high stiffness for dynamic oscillation control. This segmentation allows each substructure to optimize for its specific function without compromising the other.
Solution Approach 2:
Different regions of the measurement structure are assigned different material properties: the first substructure uses materials optimized for thermal stability (low CTE) while the second substructure uses materials optimized for mechanical stiffness. This local differentiation resolves the contradiction by allowing each region to have the quality it needs for its specific purpose.
2Stability of the object's composition
If the measurement structure uses materials with low coefficient of thermal expansion like SiSiC, then thermal stability and repetition precision are improved, but the material becomes difficult to machine and requires cooling systems
Solution Approach 1:
The measurement structure is divided into two mechanically decoupled substructures: a first substructure with low thermal expansion coefficient for long-term position stability, and a second substructure with high stiffness for dynamic oscillation control. This segmentation allows each substructure to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent employs different materials for the two substructures based on their specific requirements. The first substructure uses materials with low thermal expansion coefficients (such as ceramics or ceramic-composite materials) for thermal stability, while the second substructure uses materials with high stiffness for dynamic control. This composite approach allows optimization of each substructure for its specific function.
3Device complexity
If a single measurement structure is used for both long-term position determination and dynamic oscillation control, then device complexity is reduced, but it cannot simultaneously optimize for both thermal stability and dynamic response
Solution Approach 1:
The measurement structure is divided into two mechanically decoupled substructures: a first substructure with low thermal expansion coefficient for long-term position stability, and a second substructure with high stiffness for dynamic oscillation control. This segmentation allows each substructure to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent creates a measurement structure that serves multiple functions through its dual-substructure design. The first substructure handles long-term position determination with thermal stability, while the second substructure handles dynamic oscillation control. Both substructures work together to provide comprehensive position measurement capabilities, achieving multi-functionality while maintaining relatively simple overall structure.
4Speed
If the measurement structure has high stiffness for quick position changes, then dynamic control capability is improved, but thermal influences cause positioning errors over time
Solution Approach 1:
The measurement structure is divided into two mechanically decoupled substructures: a first substructure with low thermal expansion coefficient for long-term position stability, and a second substructure with high stiffness for dynamic oscillation control. This segmentation allows each substructure to optimize for its specific function without compromising the other.
Solution Approach 2:
Different regions of the measurement structure are assigned different material properties: the first substructure uses materials optimized for thermal stability (low CTE) while the second substructure uses materials optimized for mechanical stiffness. This local differentiation resolves the contradiction by allowing each region to have the quality it needs for its specific purpose.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the robustness of the system against thermal and magnetic influences, reducing overlay errors and improving imaging quality by allowing for more precise and accurate positioning of optical elements without the need for complex cooling systems or inaccurate mechanical models.
Implementation Method 1
the first of which has a lower coefficient of thermal expansion than the second one
Implementation Method 2
the second one has a greater stiffness than the first one
Implementation Method 3
sensors, in particular position sensors in the form of optical encoders
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a projection exposure apparatus for semiconductor lithography, comprising - a light source for generating optical used radiation by way of which structures, which are arranged on a reticle, can be imaged onto a wafer, - a plurality of optical elements (M1, M2) for guiding and manipulating the used radiation, - a plurality of position sensors (24, 25) for determining the position of at least some of the optical elements (M1, M2), - wherein at least some of the position sensors (24, 25) are arranged on a measurement structure that is at least partially decoupled mechanically and/or thermally from the further components of the projection exposure apparatus. The measurement structure has at least two mechanically decoupled substructures (22, 23) here, the first substructure (22) of which has a lower coefficient of thermal expansion than the second substructure (23), and the second substructure (23) has a greater stiffness than the first substructure (22).